This invention relates to an apparatus and method for restoring sharpness and improving the geometric shape of knives and other cutting blades. The invention may be used with many types of cutting blades but it is particularly effective with knife edges of straight, curved, circular, or cylindrical shapes with single bevel, double bevel, or modified chiseled bevel geometry.
Ideally, the edge of a cutting blade should have adjacent faces which, in cross-section, converge at a constant slope to a single point which is the ideal cutting edge vertex. In practice, however, this is rarely achieved. The slopes vary, and there is no single point of convergence. In the course of normal use of a cutting blade, the material at the edge is displaced away from the ideal vertex, changing the slopes of the faces at the edge and providing an arcuate profile at the edge. This reduces the efficiency of the cutting blade, it requires more cutting force, and it produces irregular shearing of the material being cut.
A number of devices have been proposed to restore and improve the edges of cutting blades. Some remove material by grinding or honing. Grinding creates the desired geometric shape. Honing improves the surface finish and the sharpness of the edge. These methods have minimal effect on the microstructure of the arcuate profile at the edge.
Rather than removing material, it is possible to sharpen a cutting edge by burnishing it. By using such a technique, the material is deformed to blend the curvature of the arcuate profile with the faces of the cutting blade. The present invention uses such a technique in a manner which is believed to produce results superior to those of prior burnishing devices.